The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study...The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study clarifies the relationship between radial pressure and bonding length for the ultimate pullout force and reveals the microscopic failure process of the resin-rock interface in the anchoring system.The results show that the ultimate load increases with the increase of bonding length in three different stages:rapid,slow,and uniform growth.The new mechanical model developed considering radial pressure describes the inverse relationship between radial pressure and the plastic zone on the bonding section,and quantifies the reinforcing effect of confining pressure on the anchoring force.During the pull-out process of the anchor cable,the generation of failure cracks is in the order of orifice,bottom,and middle of the hole.Radial pressure can effectively enhance the ultimate pull-out force,alleviate the oscillation increase of pull-out force,and inhibit resin cracking,but will produce an external crushing zone.It also reveals the synergistic effect between bonding length and radial pressure,and successfully carries out industrial tests of anchor cable support,which ensures the stability of the stope roof and provides an important reference for the design of anchor cable support in deep high-stress mines.展开更多
MgH_(2),albeit with slow desorption kinetics,has been extensively studied as one of the most ideal solid hydrogen storage materials.Adding such catalyst as Ni can improve the desorption kinetics of MgH_(2),whereas the...MgH_(2),albeit with slow desorption kinetics,has been extensively studied as one of the most ideal solid hydrogen storage materials.Adding such catalyst as Ni can improve the desorption kinetics of MgH_(2),whereas the catalytic role has been attributed to different substances such as Ni,Mg_(2)Ni,Mg_(2)NiH0.3,and Mg_(2)NiH4.In the present study,Ni nanoparticles(Ni-NPs)supported on mesoporous carbon(Ni@C)have been synthesized to improve the hydrogen desorption kinetics of MgH_(2).The utilization of Ni@C largely decreases the dehydrogenation activation energy from 176.9 to 79.3 kJ mol^(−1) and the peak temperature of dehydrogenation from 375.5 to 235℃.The mechanism of Ni catalyst is well examined by advanced aberration-corrected environmental transmission electron microscopy and/or x-ray diffraction.During the first dehydrogenation,detailed microstructural studies reveal that the decomposition of MgH_(2)is initially triggered by the Ni-NPs,which is the rate-limiting step.Subsequently,the generated Mg reacts rapidly with Ni-NPs to form Mg_(2)Ni,which further promotes the dehydrogenation of residual MgH_(2).In the following dehydrogenation cycle,Mg_(2)NiH4 can rapidly decompose into Mg_(2)Ni,which continuously promotes the decomposition of MgH_(2).Our study not only elucidates the mechanism of Ni catalyst but also helps design and assemble catalysts with improved dehydriding kinetics of MgH_(2).展开更多
Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to comp...Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.展开更多
Fiber-reinforced polymer(FRP)composites are increasingly popular due to their superior strength to weight ratio.In contrast to significant recent advances in automating the FRP manufacturing process via 3D printing,qu...Fiber-reinforced polymer(FRP)composites are increasingly popular due to their superior strength to weight ratio.In contrast to significant recent advances in automating the FRP manufacturing process via 3D printing,quality inspection and defect detection remain largely manual and inefficient.In this paper,we propose a new approach to automatically detect,from microscope images,one of the major defects in 3D printed FRP parts:fiber-deficient areas(or equivalently,resin-rich areas).From cross-sectional microscope images,we detect the locations and sizes of fibers,construct their Voronoi diagram,and employ-shape theory to determine fiber-deficient areas.Our Voronoi diagram and-shape construction algorithms are specialized to exploit typical characteristics of 3D printed FRP parts,giving significant efficiency gains.Our algorithms robustly handle real-world inputs containing hundreds of thousands of fiber cross-sections,whether in general or non-general position.展开更多
基金Financial supports for this work,provided by the National Natural Science Foundation Project of China(No.52374152)the Guangxi Science and Technology Plan Project of China(No.2022AB31023)the National Basic Research Development Program of China(No.2022YFC2904602)are gratefully acknowledged。
文摘The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study clarifies the relationship between radial pressure and bonding length for the ultimate pullout force and reveals the microscopic failure process of the resin-rock interface in the anchoring system.The results show that the ultimate load increases with the increase of bonding length in three different stages:rapid,slow,and uniform growth.The new mechanical model developed considering radial pressure describes the inverse relationship between radial pressure and the plastic zone on the bonding section,and quantifies the reinforcing effect of confining pressure on the anchoring force.During the pull-out process of the anchor cable,the generation of failure cracks is in the order of orifice,bottom,and middle of the hole.Radial pressure can effectively enhance the ultimate pull-out force,alleviate the oscillation increase of pull-out force,and inhibit resin cracking,but will produce an external crushing zone.It also reveals the synergistic effect between bonding length and radial pressure,and successfully carries out industrial tests of anchor cable support,which ensures the stability of the stope roof and provides an important reference for the design of anchor cable support in deep high-stress mines.
基金supported by the National Natural Science Foundation of China(Nos.22279111,51971195,and 11935004)the Natural Science Foundation of Hebei Province(No.B2020203037)Subsidy for Hebei Key Laboratory of Applied Chemistry after Operation Performance(No.22567616H).
文摘MgH_(2),albeit with slow desorption kinetics,has been extensively studied as one of the most ideal solid hydrogen storage materials.Adding such catalyst as Ni can improve the desorption kinetics of MgH_(2),whereas the catalytic role has been attributed to different substances such as Ni,Mg_(2)Ni,Mg_(2)NiH0.3,and Mg_(2)NiH4.In the present study,Ni nanoparticles(Ni-NPs)supported on mesoporous carbon(Ni@C)have been synthesized to improve the hydrogen desorption kinetics of MgH_(2).The utilization of Ni@C largely decreases the dehydrogenation activation energy from 176.9 to 79.3 kJ mol^(−1) and the peak temperature of dehydrogenation from 375.5 to 235℃.The mechanism of Ni catalyst is well examined by advanced aberration-corrected environmental transmission electron microscopy and/or x-ray diffraction.During the first dehydrogenation,detailed microstructural studies reveal that the decomposition of MgH_(2)is initially triggered by the Ni-NPs,which is the rate-limiting step.Subsequently,the generated Mg reacts rapidly with Ni-NPs to form Mg_(2)Ni,which further promotes the dehydrogenation of residual MgH_(2).In the following dehydrogenation cycle,Mg_(2)NiH4 can rapidly decompose into Mg_(2)Ni,which continuously promotes the decomposition of MgH_(2).Our study not only elucidates the mechanism of Ni catalyst but also helps design and assemble catalysts with improved dehydriding kinetics of MgH_(2).
基金National Key Research and Development Program of China(no.2021YFA1400200)National Natural Science Foundation of China(nos.12025407,11934003,and 12204513)“Strategic Priority Research Program(B)”of Chinese Academy of Sciences(grant nos.XDB330301 and YSBR047).
文摘Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.
文摘Fiber-reinforced polymer(FRP)composites are increasingly popular due to their superior strength to weight ratio.In contrast to significant recent advances in automating the FRP manufacturing process via 3D printing,quality inspection and defect detection remain largely manual and inefficient.In this paper,we propose a new approach to automatically detect,from microscope images,one of the major defects in 3D printed FRP parts:fiber-deficient areas(or equivalently,resin-rich areas).From cross-sectional microscope images,we detect the locations and sizes of fibers,construct their Voronoi diagram,and employ-shape theory to determine fiber-deficient areas.Our Voronoi diagram and-shape construction algorithms are specialized to exploit typical characteristics of 3D printed FRP parts,giving significant efficiency gains.Our algorithms robustly handle real-world inputs containing hundreds of thousands of fiber cross-sections,whether in general or non-general position.
